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https://issues.apache.org/jira/browse/HADOOP-6232?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12750400#action_12750400
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Vinod K V commented on HADOOP-6232:
-----------------------------------
This is mostly a timing issue and happens when memory manager tries to destroy
a process that is just gone. It didn't affect the testcase. The memory manager
code doesn't propagate failures across its processing of multiple tasks. The
side-effects seem to be mostly negligible. As we try to remove a task entry
from the processTreeInfoMap map only after destroy succeeds. I think a task
entry will be left in the map, but as we enough null checks in place, this
process will just be skipped in further iterations.
> NPE in ProcfsBasedProcessTree.destroy()
> ---------------------------------------
>
> Key: HADOOP-6232
> URL: https://issues.apache.org/jira/browse/HADOOP-6232
> Project: Hadoop Common
> Issue Type: Bug
> Reporter: Vinod K V
> Priority: Minor
>
> This causes the following exception in TaskMemoryManagerThread. I observed
> this while running TestTaskTrackerMemoryManager.
> {code}
> 2009-09-02 12:08:25,835 WARN mapred.TaskMemoryManagerThread
> (TaskMemoryManagerThread.java:run(239)) - Uncaught exception in
> TaskMemoryManager while managing memory of
> attempt_20090902120812252_0001_m_000003_0 : java.lang.NullPointerException
> at
> org.apache.hadoop.util.ProcfsBasedProcessTree.assertPidPgrpidForMatch(ProcfsBasedProcessTree.java:234)
> at
> org.apache.hadoop.util.ProcfsBasedProcessTree.assertAndDestroyProcessGroup(ProcfsBasedProcessTree.java:257)
> at
> org.apache.hadoop.util.ProcfsBasedProcessTree.destroy(ProcfsBasedProcessTree.java:286)
> at
> org.apache.hadoop.mapred.TaskMemoryManagerThread.run(TaskMemoryManagerThread.java:229)
> {code}
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